This invention generally relates to human hair growth and, more particularly, to methods and devices for stimulating hair growth through stimulation of the hair follicles by means of a laser.
Alopecia (hair loss) is a major concern for the adult population. Expenditures for hair restoration products and treatments for hair loss represent a major component of the multibillion-dollar cosmetic industry in the United States. Examples of techniques for hair retention and regeneration include the use of hair weaving, the use of hairpieces, the application of hair thickening sprays and shampoos, hair transplantation, and the fashioning of coiffures which distribute hair to cover balding regions of the scalp. In addition, topical drug therapies, such as Minoxidil (Rogaine®) or oral drug therapies such as Finasteride (Propecia®), are in current use to stimulate hair growth in men suffering from male pattern baldness, i.e. baldness occurring at the crown and temples. However, this chemical cannot be used by women, can cause a negative skin reaction on the scalp, and is, therefore, not suitable for everyone, and efficacy is limited and not universal.
Diode laser systems have been developed for various medical treatments of the human body. See for example, Applicant's prior U.S. Pat. Nos. 5,755,752 and 6,033,431, which are both incorporated herein by reference in their entirety. Depending on the type of treatment desired, lasers of various wave lengths, periods of exposure and other such influencing factors have been developed.
Lasers are the newest surgical tool for the medical profession because laser light, as a result of its monochromatic and coherent nature, can be selectively absorbed by living tissue. The absorption of the optical energy from laser light depends upon certain characteristics of the wavelength of the light and properties of the irradiated tissue, including reflectivity, absorption coefficient, scattering coefficient, thermal conductivity, and thermal diffusion constant. The reflectivity, absorption coefficient, and scattering coefficient are dependent upon the wavelength of the optical radiation. The absorption coefficient is known to depend upon such factors as interband transition, free electron absorption, grid absorption (photon absorption), and impurity absorption, which are also dependent upon the wavelength of the optical radiation.
In living tissue, the predominant water component has an absorption band determined by the vibration of water molecules. In the visible portion of the spectrum, there exists absorption due to the presence of hemoglobin. Further, the scattering coefficient in living tissue is a dominant factor.
Thus, for a given tissue type, the laser light may propagate substantially unattenuated through the tissue, or may be almost entirely absorbed. The extent to which the tissue is heated and ultimately destroyed depends on the extent to which it absorbs the optical energy and the power associated with the energy. It is generally preferred that the laser light be essentially transmissive through tissues which are not to be affected, and absorbed by tissues which are to be affected. For example, when applying laser radiation to a region of tissue permeated with water or blood, it is desired that the optical energy not be absorbed by the water or blood, thereby permitting the laser energy to be directed specifically to the tissue to be treated. Another advantage of laser treatment is that the optical energy can be delivered to the treatment tissues in a precise, well defined location and at predetermined, limited energy levels.
Ruby and argon lasers are known to emit optical energy in the visible portion of the electromagnetic spectrum, and have been used successfully in the field of opthalmology to reattach retinas to the underlying choroidea and to treat glaucoma by perforating anterior portions of the eye to relieve interoccular pressure. The ruby laser energy has a wavelength of 694 nanometers (nm) and is in the red portion of the visible spectrum. The argon laser emits energy at 488 nm and 515 nm and thus appears in the blue-green portion of the visible spectrum. The ruby and argon laser beams are minimally absorbed by water, but are intensely absorbed by blood chromogen hemoglobin. Thus, the ruby and argon laser energy is poorly absorbed by non-pigmented tissue such as the cornea, lens and vitreous humor of the eye, but is absorbed very well by the pigmented retina where it can then exert a thermal effect.
Another type of laser which has been adapted for surgical use is the carbon dioxide (CO2) gas laser which emits an optical beam that is well absorbed by water. The wavelength of the CO2 laser is 10,600 nm and therefore lies in the invisible, far infrared region of the electromagnetic spectrum. It is absorbed independently of tissue color by all soft tissues having a high water content. Since it is completely absorbed, the CO2 laser makes an excellent surgical scalpel and vaporizer since its depth of penetration is shallow and can be precisely controlled with respect to the surface of the tissue being treated.
Another laser in widespread use is the neodymium doped yttrium-aluminum-garnet (Nd:YAG) laser. The Nd:YAG laser has a predominant mode of operation at a wavelength of 1064 nm in the near infrared region of the electromagnetic spectrum. The Nd:YAG optical emission is absorbed to a greater extent by blood than by water making it useful for coagulating large, bleeding vessels. The Nd:YAG laser has been transmitted through endoscopes for treatment of a variety of gastrointestinal bleeding lesions, such as esophageal varices, peptic ulcers, and arteriovenous anomalies.
The foregoing applications of laser energy are thus well-suited for use as a surgical scalpel and in situations where high energy thermal effects are desired, such as tissue vaporization, tissue cauterization, and coagulation.
Although the foregoing laser systems perform well, they commonly generate large quantities of heat and require a number of lenses and mirrors to properly direct the laser light and, accordingly, are relatively large, unwieldy, and expensive. As such, they are unsuitable for use in stimulating hair growth.
Lasers are in increasing use to effect hair removal. This is done by overheating the hair follicles to destroy them. Recently, laser treatment has now been developed specifically for use as a positive stimulating agent for hair growth. The alleged key is to use low power lasers, so as not to destroy, but stimulate the follicles. Several patents have addressed this solution in different way. For example, see U.S. Pat. Nos. 6,497,719, 6,666,878, and 6,802,853. A commercial system similar to that disclosed in the '878 patent uses an array of circumferentially-spaced parallel rows of laser diodes in a hair-dryer type apparatus which rotates. These diodes are carefully arrayed in adjacent rows of staggered diodes to assure overlapping of the light fields of adjacent diodes. The prescribed diodes have a wave length of 400 to 1300 nm (670 nm preferred) and a power sufficient to generate a power density of 7-8 joules/cm2. The various embodiments require dozens or even hundreds of diodes. These commercial units are quite expensive and retail for $25,000-$30,000, which severely limits its market and consequent availability to the public for hair growth treatment.
As can be seen, there is a need for a simpler and lower cost system and method for stimulating hair growth with laser energy without damaging the tissue from the thermal effects of the laser energy.